Projectile

ABSTRACT

A projectile ( 100 ) is provided for operating at least in a launch phase and in a post-launch phase. The projectile includes a projectile body ( 10 ), a projectile head ( 50 ), and a support structure ( 80 ). The projectile head is non-rigidly mounted to the projectile body via a joint structure ( 70 ). The support structure is configured for selectively supporting the projectile head with respect to the projectile body in a load bearing relationship independently of the joint structure during at least a portion of the launch phase, and for selectively terminating the support during at least a portion of the post-launch phase. A method for operating a projectile and a method for retrofitting a projectile are also provided.

FIELD OF THE INVENTION

This invention relates to projectiles, especially shells, in particular for use in mortars or other high launch-acceleration applications.

BACKGROUND OF THE INVENTION

By way of general background, the following publications disclose a variety of projectile or air vehicle configurations: U.S. Pat. No. 4,533,094; US 2010/0057285; US 2008/0276821; U.S. Pat. No. 4,938,434; U.S. Pat. No. 4,541,591.

The contents of these references are incorporated herein in their entirety.

SUMMARY

According to a first aspect of the invention, there is provided an air vehicle, for example in the form of a projectile configured for operating at least in a first traveling phase and in a second traveling phase.

By traveling of the vehicle is meant the motion of the vehicle through a fluid medium or a vacuum, in particular Earth's atmosphere or through space as a free body. By free motion of the vehicle is meant the motion of the vehicle through a, fluid medium or a vacuum, in particular Earth's atmosphere or space as a free body, while unsupported on the ground, either directly or indirectly, or unsupported within another vessel that is itself traveling through the fluid medium or vacuum. In at least one example the first traveling phase is a launch phase and the second traveling phase is a post-launch phase, and at least in the post-launch phase the vehicle is in free motion.

The air vehicle or projectile comprises:

-   -   a projectile body, a projectile head, and a support structure,     -   wherein said projectile head is non-rigidly mounted to said         projectile body via a joint structure; and     -   wherein said support structure is configured for selectively         supporting said projectile head with respect to said projectile         body in a load bearing relationship independently of said joint         structure during at least a portion of (or all of) said launch         phase (or said first traveling phase), and for selectively         terminating said support during at least a portion of said         post-launch phase (or said second traveling phase).

In particular, the air vehicle or projectile is configured for selectively terminating said support during said at least a portion of said post-launch phase (or said second traveling phase), wherein the air vehicle or projectile is in free motion.

The air vehicle or projectile can have one or more of the following features, in any desired combination or permutation.

In at least some embodiments, said projectile head is pivotably mounted to said projectile body via said joint structure.

Additionally or alternatively, said projectile head is axially movable with respect to said projectile body via said joint structure at least in when said support is terminated. For example, said projectile head is axially movable with respect to said projectile body via said joint structure in the absence of said support.

Additionally or alternatively, said projectile head is configured for being freely aerodynamically aligned with said velocity vector of the projectile independently of said projectile body (e.g. in the absence of said support structure) when said support is terminated.

Additionally or alternatively, said support structure is configured for preventing at least a majority of loads between said projectile head and said projectile body associated with said launch phase being channeled via (or supported by) said joint structure. For example, said majority of said loads is otherwise damaging if applied to said joint structure. For example, said majority comprises more than 50% of said loads.

Additionally or alternatively, said projectile body comprises a front end, an aft end and a first longitudinal axis extending therebetween, and wherein said projectile head comprises a second longitudinal axis, wherein in said load bearing relationship, said first longitudinal axis is substantially coaligned with said second longitudinal axis. Alternatively, the first longitudinal axis is parallel to but not co-aligned with said second longitudinal axis. Optionally, the air vehicle or projectile may comprise a plurality of said projectile heads mounted to said projectile body, each via a respective said joint structure.

Additionally or alternatively, in said load bearing relationship, said support structure externally supports said projectile head with respect to said projectile body. For example, said support structure supports said projectile head with respect to said projectile body on an outside of the projectile body.

Additionally or alternatively, in said load bearing relationship, said support structure reversibly interconnects said projectile head with said projectile body and is configured for supporting said loads between said projectile head and said projectile body when thus interconnected.

Additionally or alternatively, said support structure is configured for being removed from said projectile body and said projectile head at least during said portion of said post-launch phase for selectively terminating said support.

Additionally or alternatively, said loads are induced responsive to an acceleration of the projectile during said launch phase (or said first traveling phase). For example, such loads may be in the order of 10⁴*W, where W is the mass of the projectile head.

Additionally or alternatively, said support structure is further configured for preventing aerodynamic loads being directly applied to said projectile head during said portion of said launch phase and optionally until the support is terminated. For example, said support structure is configured for shielding the projectile head from aerodynamically-induced loads.

Additionally or alternatively, said support structure comprises a load bearing member, wherein in said load bearing relationship said load bearing member is in load bearing contact with said projectile body and in load bearing contact with an external part of said projectile head.

Additionally or alternatively, said support structure comprises a housing having an open aft end and a cavity in communication therewith, wherein said aft end is configured for reversibly connecting to said projectile body and wherein said cavity is configured for accommodating said projectile head therein in load bearing contact therewith.

Additionally or alternatively, at least during said portion of said post-launch phase (or of said second traveling phase) said projectile head is freely pivotable with respect to said projectile body in at least one rotational degree of freedom.

Additionally or alternatively, at least during said portion of said post-launch phase (or of said second traveling phase) said projectile head is freely pivotable with respect to said projectile body in at least two rotational degrees of freedom.

Additionally or alternatively, at least during said portion of said post-launch phase said projectile head is freely pivotable with respect to said projectile body in three rotational degrees of freedom.

Additionally or alternatively, said joint structure is configured for permitting relative angular movement between said projectile head and said projectile body, said projectile head being configured for self-alignment with a free stream fluid flow direction, of a fluid through which said projectile is traveling, via said joint structure in said post-launch phase, wherein said projectile head is exposed to the fluid flow.

Additionally or alternatively, said projectile head is gimbaled freely to said projectile body via said joint structure. Alternatively, said joint structure comprises a flexible hose.

Additionally or alternatively, said projectile head comprises an aft portion comprising an annular tail airfoil, configured for providing said self-alignment.

Additionally or alternatively, said projectile head is configured for homing said projectile to a target.

Additionally or alternatively, said projectile body further comprises a steering arrangement configured for steering the projectile responsive to suitable control input; and said projectile head is further configured for providing said control input at least during said portion of said post-launch phase. The projectile head can comprise a suitable sensor arrangement configured for sensing a control parameter wherein to generate said control input in response thereto. The sensor arrangement can be provided at a forward end of said projectile head. The sensor arrangement can be configured for sensing a predetermined illuminating electromagnetic radiation wherein to generate said control input in response thereto. The steering arrangement can comprise an aerodynamic control surface arrangement configured for generating aerodynamic moments suitable for steering said projectile, responsive to said control input. The aerodynamic moments can include one or more of pitch, yaw and roll. Optionally, the aerodynamic control surface arrangement can comprise a plurality of canards, said canards being individually controllable to selectively generate said aerodynamic moments. Optionally, the canards can be deployable from a stowed configuration to a deployed configuration, and wherein said canards are in said stowed configuration at least during said portion of said launch phase. Optionally, the canards can be in said deployed configuration at least during said portion of said post-launch phase. Optionally, the sensor arrangement can comprise a plurality of sensors operatively connected to said plurality of canards, each said sensor being configured for generating a control signal for operating a respective said canard.

Additionally or alternatively, the air vehicle or projectile further comprises a plurality of aft fins for providing longitudinal stability at least during said portion of said post-launch phase. For example, the aft fins can be deployable from a stowed configuration to a deployed configuration, and wherein said aft fins are in said stowed configuration at least during a part of said portion of said launch phase.

Additionally or alternatively, said projectile can be configured for being having a maximum width not greater than a maximum width of said projectile body at least during a part of said portion of said launch phase.

Additionally or alternatively, said support structure comprises a casing having an aerodynamically contoured outer wall, and an internal seat for seating an aft portion of said projectile head in said load bearing relationship. For example, in said load bearing relationship, said projectile head can be immobilized in said casing. Optionally, in said load bearing relationship, the casing substantially prevents axial displacement between said projectile head and said projectile body. Optionally, in said load bearing relationship, said projectile head and said projectile body are longitudinally aligned. Optionally, said casing comprises a first casing half reversibly joined to a second casing half. For example, said support structure is removable from said projectile head and said projectile body by separating said first casing half from said second casing half.

Additionally or alternatively, said support structure is selectively jettisonable from said projectile.

Additionally or alternatively, said projectile is configured as a mortar shell configured to be launched via a mortar.

According to the first aspect of the invention there is also provided a projectile configured for operating at least in a high-g launch phase and a low-g post-launch phase, comprising:

-   -   a projectile body, a projectile head, and a selectively         removable support structure,     -   said projectile head being non-rigidly mounted to said         projectile body via a joint structure;     -   said support structure configured for selectively connecting         said projectile body and said projectile head in a load bearing         relationship independently of said joint structure, when the         projectile is subject in operation of said projectile during at         least a portion of said launch phase; and     -   said projectile head being configured for being freely         aerodynamically aligned with a velocity vector of the projectile         independently of said projectile body (in the absence of said         support structure) in operation of said projectile during at         least a portion of said post-launch phase wherein said load         bearing relationship is terminated.

According to the first aspect of the invention there is also provided a method for operating a projectile, comprising:

-   -   (a) providing a projectile or air vehicle as defined above         including one or more of the above features in any desired         combination or permutation;     -   (b) operating said projectile or air vehicle during at least         said portion of said launch phase (or said first traveling         phase) wherein to selectively support said projectile body with         respect to said projectile head via said support structure in a         load bearing relationship independently of said joint structure;     -   (c) selectively terminating said load bearing relationship and         subsequently operating said projectile or air vehicle during at         least said portion of said post-launch phase (or second         traveling phase).

In at least some embodiments, step (c) comprises removing said support structure from said projectile head and said projectile body while said projectile is traveling in the atmosphere, and allowing said projectile body to become freely aerodynamically aligned with a velocity vector of the projectile independently of said projectile body.

Additionally or alternatively, the method also comprises homing said projectile to a target. Optionally, the method further comprises illuminating said target with an illuminating radiation, detecting with said projectile head said illuminating radiation reflected from the target, and steering said projectile to said target wherein to maintain said reflected illuminating radiation in the boresight of said projectile head.

According to the first aspect of the invention there is also provided a method for retrofitting a projectile or air vehicle, comprising:

-   -   (a) providing the projectile or air vehicle, the projectile or         air vehicle comprising a projectile body and a projectile head,         wherein the projectile head is non-rigidly mounted to the         projectile body via a joint structure; and     -   (b) providing a selectively removable support structure, wherein         said support structure is configured for selectively supporting         said projectile head with respect to said projectile body in a         load bearing relationship independently of said joint structure         during at least a portion of said launch phase, and for         selectively terminating said support during at least a portion         of said post-launch phase.

Additionally or alternatively, the projectile head, the projectile body, the joint structure and the support structure may be as defined above, mutatis mutandis, including one or more of the above features mutatis mutandis, in any desired combination or permutation.

For example, said support structure is configured for preventing at least a majority of loads between said projectile head and said projectile body associated with said launch phase (or said first traveling phase) being channeled via (or supported by) said joint structure, and optionally wherein said majority of said loads is otherwise damaging if applied to said joint structure.

According to a second aspect of the invention there is provided a projectile or air vehicle, comprising:

-   -   a projectile body and a projectile head;     -   wherein said projectile head is non-rigidly mounted to said         projectile body via a joint structure at a forward end of the         projectile body; and     -   wherein said projectile is configured for permitting limited         relative axial movement between said projectile body and said         projectile head via said joint structure.

Additionally or alternatively, the projectile head, the projectile body, and the joint structure may be as defined above for the first aspect of the invention, mutatis mutandis, including one or more of the above features for the first aspect of the invention mutatis mutandis, in any desired combination or permutation.

Additionally or alternatively, the projectile or air vehicle may further comprise a support structure as defined above for the first aspect of the invention, mutatis mutandis, including one or more of the above features for the first aspect of the invention mutatis mutandis, in any desired combination or permutation.

Additionally or alternatively, said joint structure comprises a forward portion configured for pivotingly mounting said projectile head thereto, and an aft portion comprising a shaft slidingly mounted to said projectile body. For example, said shaft is axially reciprocably movable with respect to said projectile body within a displacement range. Optionally a resilient member can be provided for biasing said shaft with respect to said projectile body. As in the first aspect of the invention, mutatis mutandis, the projectile head can be configured for self-alignment with a free stream fluid flow direction, of a fluid through which the projectile is traveling, via said joint structure, when the projectile head is exposed to the fluid flow. For example, the projectile head can comprise an aft portion comprising an annular tail airfoil, configured for providing said self-alignment.

BRIEF DESCRIPTION OF THE FIGURES

In order to understand the invention and to see how it may be carried out in practice, several embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation illustrating in side view a projectile according to an embodiment of the invention, including a support structure supporting the projectile head on the projectile body.

FIG. 2 is a detailed view of FIG. 1.

FIG. 3 is a schematic representation illustrating in side view the embodiment of FIG. 1, wherein the support structure is removed.

FIG. 4 is a detailed view of FIG. 3.

FIG. 5 is a schematic representation illustrating an example of operation of the embodiment of FIGS. 1 to 4.

DETAILED DESCRIPTION OF THE FIGURES

Referring to FIGS. 1 to 4, an air vehicle according to a first embodiment of the invention is generally designated with reference numeral 100 and comprises a body 10 and head 50, and further comprises a support structure 80.

In the illustrated example, the air vehicle 100 is particularly configured as a projectile in the form of a mortar round, or the like, for traveling through the atmosphere when launched, though the skilled practitioner appreciates that at least some embodiments of the invention are also applicable, mutatis mutandis, to other types of projectiles, including cannon-launched shells, self-propelled missiles, rockets, rocket payloads (e.g. satellites, etc.), non-air vehicles configured for operating in partly or fully in space, for example, and the like, mutatis mutandis, having relatively high launch acceleration loads at the launch phase (also referred to herein as the first traveling phase). Accordingly, the term “air vehicle” is taken herein to include any suitable air vehicle that is subjected to relatively high launch acceleration or high acceleration at a first traveling phase, for example (but not limited to) corresponding to projectile launched from cannons, mortars etc, for example (but not limited to) in the order of 10⁴*g, where “g” is the acceleration due to gravity, and which also operates by traveling freely, i.e. in free motion, through a fluid medium (such as the Earth's atmosphere, for example) or in space in a post-launch phase (also referred to herein as the second traveling phase) in which it is subject to much lower acceleration loads, or no such loads at all.

In this example, the projectile does not comprise any propulsion unit or powerplant and receives its forward momentum from a mortar (or in alternative embodiments, from a cannon or the like, i.e., a launch system that is configured to impart to the projectile a forward momentum and acceleration at launch). However, in alternative variations of this embodiment, the projectile 100 may be configured with a propulsion unit or powerplant, such as for example one or more of a rocket motor, ramjet, turbojet and so on, which may be integral for example, for providing propulsion to the projectile 100, and/or including for example an ejectable rocket propulsion unit, to impart forward acceleration and velocity to the projectile 100.

Body 10 comprises an elongate fuselage 19 having a longitudinal centerline or axis A. The fuselage 19 comprises a nose or front end 11, middle section 12, and an aft end 13, and may comprise a generally circular cross-section along at least a majority of its length along the axis A. In alternative variations of this embodiment, the fuselage 19 may comprise a non-circular cross-section, for example oval, polygonal etc., and may optionally comprise a faceted outer surface.

The nose or front end 11 may comprise a relatively pointed or rounded or otherwise aerodynamically contoured profile, and includes a bore 18 aligned with axis A and open at the forward end, the purpose of which shall become clearer below.

Referring in particular to FIG. 3, the middle section 12 comprises a forward portion 12 a of generally constant cross-section, and defining a maximum width or diameter D, and a tapering aft portion 12 b that connects to the aft end 13. The middle section 12 defines a payload chamber 14 that houses an explosive charge as well as at least a part of the mechanism that is used for priming and detonating the explosive charge. In alternative variations of this embodiment, the payload chamber may accommodate other materials, equipment or objects.

Aft end 13 comprises eight fins 20, radially radiating from the axis A, and uniformly spaced with respect to one another. The fins 20 are configured for providing longitudinal and lateral stability, and are pivotably deployable about the respective pivot axes 22, from a retracted or stowed configuration marked in phantom lines as 20′, in which the spans S of the fins 20 are generally parallel to axis A and the tips of the vanes 20 are forward of the respective pivot axes 22, to a deployed configuration, in which the spans S of the fins 20 are swept back at a modest sweep angle with respect to an imaginary plane that is orthogonal to the axis A. In the retracted configuration, the vanes 20 are enclosed within an envelope defined by the aforesaid maximum diameter D.

In alternative variations of this embodiment, the aft end 13 may comprise less than eight fins or more than eight fins and/or any other suitable configuration for providing longitudinal and lateral stability.

The projectile 100 further comprises a direction control mechanism 40 comprising four control canards 30, in cruciform “X” or “+” arrangement, in which the canards 30 are essentially divided into two pairs of canards, wherein in each pair the respective canards 30 are arranged in diametrical opposed relationship with respect to axis A. and are configured for providing steering control of the vehicle 100, in particular control of one or more of the pitch, yaw and roll of the body 10, responsive to control inputs generated by the head 50, as will be disclosed in greater detail below. In alternative variations of this embodiment, the vehicle may comprise less than four or more than four canards, and/or any other suitable configuration for enabling the air vehicle to be steered responsive to said control input or other suitable steering input.

The canards 30 are pivotably deployable about the respective pivot axes 32, from a retracted or stowed configuration shown in FIGS. 1 and 2 (and also marked in phantom lines as 30′ in FIGS. 3 and 4), to a deployed configuration illustrated in FIGS. 3 and 4. In the stowed configuration, and as best seen in FIG. 4, the spans Q of the respective canards 30 are generally parallel to axis A, the tips of the canards 30 are forward of the respective pivot axes 32, and the canards 30 are accommodated in complementary radial slots 34 provided in the front end 11. In the stowed configuration, the canards 30 are configured to be enclosed within an envelope defined by the aforesaid maximum diameter D.

In the deployed configuration, the spans Q of the canards 30 are swept back at a modest sweep angle with respect to an imaginary plane that is orthogonal to the axis A, and are located close the front end of the middle section 12. In alternative variations of this embodiment, other retracted and/or deployed configurations may be provided, or the canards may be permanently deployed.

Pivot axes 32 are orthogonal to and do not intersect the axis A, and each pivot axis is generally orthogonal to the span Q of the respective canard 30.

The direction control mechanism 40 further comprises a canard actuation arrangement in the form of a servo assembly 45. The servo assembly 45 is configured for actuating each opposed pair of canards 30 (responsive to control inputs generated by the head 50), when the canards 30 are in the deployed configuration, independently of one another, to pivot each canard 30 of the respective pairs in the same or opposite direction to the other canard of the same pair, about the respective actuation axis B, radially projecting orthogonally from axis A, to provide suitable control moments in one or more of pitch, yaw and roll. The respective actuation axes B for a first pair of opposed pair of canards 30 are co-axially aligned, while the respective actuation axes B for a second pair of opposed pair of canards 30 are co-axially aligned, but orthogonal to the respective actuation axes B of the first pair of opposed pair of canards 30, and thus the two pairs of axes B are thus also in the above mentioned cruciform “X” or “+” arrangement.

In this embodiment, the respective actuation axes B for the first pair of opposed pair of canards 30 are aligned with the pitch axis P of the vehicle 100, while the respective actuation axes B of the second pair of opposed pair of canards 30 are aligned with the yaw axis Y of the air vehicle 100. In alternative variations of this embodiment, the actuation axes B may be inclined at any desired angle with respect to the pitch and yaw axes of the air vehicle, and actuation of each pair of opposed canards 30 provides a component of yaw and/or a component of pitch.

One or both pairs of opposed canards 30 may be actuated to provide roll about axis A in one or the other direction.

There are many examples in the art of suitable configurations for servo assembly 45, and this will not be described in further detail herein.

A suitable thermal battery 49 provides power to the projectile 100, including head 50 and servo assembly 40, and is accommodated in an aft part of chamber 79. The chamber 79 is forward of the payload chamber 14, and a forward end of chamber 79 is open to bore 18, which is of smaller cross-section than chamber 79. In alternative variations of this embodiment, other suitable power sources may be provided.

Referring in particular to FIG. 4, the head 50 is configured as a seeker head and comprises a head housing 52 with a forward portion 51 accommodating a sensor arrangement 60. The aft portion 53 of the head 50 comprises an internal chamber 56 having an aft-open end, and comprises a ring or annular tail airfoil 54, joined to the external part of aft portion 53 via rigid vanes 55. The head 50 has a longitudinal axis a. The maximum outer diameter of the head 50 (defined at the annular tail airfoil 54) is less than D, and thus the head 50 is within the aforesaid envelope.

The head 50 is non-rigidly, i.e. freely, mounted to body 10 via joint structure 70, at the forward end 71 of connecting shaft 72 that projects forward of the nose section 11 from the bore 18. The aft end 73 of shaft 72 is accommodated in bore 18, and has an enlarged aft end 76 axially reciprocably movable within a forward part of chamber 79, allowing for limited axial movement between shaft 72 and the bore 18 and chamber 79, and thus allowing for corresponding limited axial movement between head 50 and the projectile body 10. This axial movement is schematically indicated at “k” in FIG. 2.

A biasing resilient member in the form of compression spring 78 is provided between the battery 49 and enlarged end 76, and provides limited resistance to aft movement of shaft 72 with respect to the body 10, and the resilience of the spring 78 provides a restoring force in the forward direction.

Joint structure 70 (including shaft 72) is configured to allow free relative pivotal movement between the head 50 and the body 10 in three rotational degrees of freedom and limited movement in one degree of freedom. In particular, the joint structure 70 itself is configured for allowing free relative pivotal movement between the head 50 and the body 10 in two rotational degrees of freedom, while the shaft 72 allows for free relative pivotal movement between the head 50 and the body 10 in a third rotational degree of freedom, and limited translational movement in one degree of freedom. In alternative variations of this embodiment, the joint structure 70 may be rotatably mounted to shaft 72, and thus allows for free relative pivotal movement between the head 50 and the body 10 in three rotational degrees of freedom, while the shaft 72 provides limited translational movement in one degree of freedom. In yet other alternative variations of this embodiment the free pivotal movement between the head 50 and the body 10 may be in one degree of freedom only, or in two degrees of freedom only.

In other words, while axis a of head 50 is nominally coaxially aligned with axis A of the body 10, axis a may be freely inclined with respect to axis A in one, two or three rotational degrees of freedom. The extent of this relative pivotal movement is limited by collision between the aft end 58 of the annular tail airfoil 54 with the nose section 11, or collision of the aft edge 57 of housing 52 with shaft 72, or collision of the aft edge 57 of housing 52 with the nose section 11.

The joint structure 70 is accommodated in chamber 56, and is in the form of free gimbals in this embodiment, comprising a set of inner gimbals 74 mounted to the head 50 and defining a first pivoting axis, and orthogonally connected to a set of outer gimbals 75 that are mounted at end 71 and defining a second pivoting axis orthogonal to the first pivoting axis. In alternative variations of this embodiment the joint structure 70 may comprise any other suitable arrangement that permits the aforesaid free pivotal movement between the head 50 and the body 10 in three degrees of freedom, for example via flexible hose.

The head 50 is thus configured for automatic alignment with the velocity vector of the vehicle 100, due to the aerodynamic forces acting thereon, in particular the annular tail airfoil 54, when exposed to the freestream of the fluid (typically atmospheric air) in which the projectile 100 is traveling.

In this embodiment, the sensor arrangement 60 is configured for homing onto a target that is illuminated by a laser, typically from another source, and for providing suitable control signals to the direction control mechanism 40 for operation thereof to maintain the vehicle 100 in a suitable trajectory to the target. In this embodiment the sensor arrangement 60 comprises a four quadrant detector, in which four laser detectors are arranged in maltese cross arrangement. Each sensor is operatively connected to a different one of said canards 30 of the direction control mechanism 40, and thus provides a suitable control signal for controlling operation thereof, and thus operation of the respective canard. In operation of the sensor arrangement 60, a laser radiation transparent dome 59 focuses laser light, reflected from the illuminated target, onto the sensors. When the head 50 is boresighted on the target, i.e., the axis a of the head is pointing directly to the target, the reflected radiation received from the target is uniformly sensed by all four sensors, and each generates a similar control signal to the direction control mechanism 40, which effects no changes to the positions of the canards 30, and thus the projectile continues along the same direction. On the other hand, if the head 50 is off-target, the reflected laser light will be more focused on one or more sensors than on the other sensors, and the unequal distribution of sensed reflected light generates unequal control signals, in a ratio proportional to the off-boresight angle, to the control the direction control mechanism 40. In other words, a different control signal (also referred to herein as error signal) is generated corresponding to each quadrant, which is fed to each respective canard actuator to control actuation thereof.

In this embodiment, a proportional control loop is used, in which the amount of deflection applied to each respective canard 30 about its respective pivot axis B, is proportional to the respective error or control signal generated by the respective sensor, and thus each canard 30 may be controlled to correct the velocity vector of the vehicle 100 to align the head 50 with the target. In alternative variations of this embodiment, a simple non-proportional control loop may be used (often referred to as “bang-bang”), which results in either zero deflection or full deflection of the respective canard.

In alternative variations of this embodiment the sensor arrangement may comprise, additionally or alternatively, other sensors such as radar, other electro-optic sensors, surveillance equipment, communication means and so on, which may be housed in the head 50 and/or body 10, for example.

The projectile 100 further comprises said support structure 80, configured for selectively supporting high-g thrust loads (also referred to herein as compressive loads or acceleration loads) between the head 50 and the body 10, so that none, or at least no significant part, of these loads is effectively resisted or channeled via the joint structure 70 during the high-g launch phase (also referred to herein as the firing phase) of the projectile. The support structure 80 is further configured for selectively disengaging from at least one of the head 50 and body 10 so that at least during part of the post-launch phase when the projectile is in free motion, the head 50 is freely movable with respect to the body 10 and thus the head 50 is mechanically connected to the body 10 only via joint structure 70, and thus shaft 72.

These thrust loads are essentially the inertial loads of the head, and are determined from the product M*G, wherein M is the mass of the head 50, and G is the acceleration of the vehicle 100.

In other words, during at least a part of the high-g launch phase, the support structure 80 is configured for transferring these nominally axial acceleration loads between the head 50 and body 10, and thus effectively mechanically isolates the joint structure 70 from these loads. In other words, the support structure 80 is configured for directing acceleration loads from the head 50 to the body 10 while minimizing or eliminating stress on the joint structure 70 otherwise arising from such loads.

The support structure 80 is positioned on the outside of the body 10 and is mechanically connected to the head 50. The support structure 80 and the head 50 thus define a load bearing unit that provides a load path to the body 10 that is substantially independent of the joint structure 70, or indeed of the shaft 72. This load bearing unit is configured to react the aforesaid acceleration loads such that the support structure 80 accepts the acceleration load provided by the head 50 and carries the acceleration load in compression to the body 10, and such that the joint structure 70 is substantially isolated from and does not react at all, or to any significant extent to the acceleration loads. By “significant extent” is meant that the joint structure 70 is free or otherwise shielded from any damage arising due to the launch acceleration.

Thus, and referring in particular to FIGS. 3 and 4, the support structure 80 in this embodiment is in the form of a fairing 90, defining an internal cavity 92 and comprising a load-bearing interface 93 configured for connection with the forward end of forward portion 12 a in a load-bearing manner therewith. The fairing 90 comprises an internal shoulder 95 configured for axially supporting the annular tail airfoil 54, in particular via the aft end 58, in a load bearing manner, while concurrently aligning axis a with axis A. The internal cavity 92 also provides a close lateral fit with the annular tail airfoil 54, and thus the support structure 80 is configured for externally restraining the head 50 and preventing relative moment between the head 50 and the body 10, while not being mechanically connected to or interacting with joint structure 70.

The fairing 90 is aerodynamically contoured externally to reduce drag and to isolate the head 50 from aerodynamically induced loads while the fairing is connected to the body 10 and the projectile 100 is in forward flight. Furthermore, while the fairing is connected to the body 10, acceleration loads on the head 50 are reacted through the fairing 90 (via load-bearing contact between the annular tail airfoil 54 and the internal shoulder 95), and to the body 10 (via load-bearing contact between interface 93 of fairing 90 and interface 94 of body 10), and not through the joint structure 70.

The limited axial movement k between the head 50 and body 10 allows for the fairing 90 to be manufactured without the need for tight tolerances between the actual and relative positions of the interface 93 and internal shoulder 95 on the one hand, and the actual and relative positions of the interface 94 and the aft end 58 on the other hand. Thus, prior to subjecting the vehicle 100 to any acceleration, there may be a small axial gap between the aft end 58 and internal shoulder 95, with the interfaces 93 and 94 in contact with one another. However, when subjected to acceleration loads, the head 50 may translate in an aft direction with respect to the body 10 responsive to the acceleration, until there is load bearing contact between the aft end 58 and internal shoulder 95, the enlarged aft end 76 pressing against and compressing the spring 77. Once the acceleration loads are removed (as the vehicle decelerates, for example), the head 50 translates back in a forward direction with respect to the body 10 due to the spring 77.

The fairing 90 is also configured for being selectively disengaged from the body and head 50. The fairing 90 is formed from two lateral fairing halves, 90A, 90B, joined at a plane W that is parallel to and intersects the aligned axes a and A. The fairing halves, 90A, 90B are held together during the load-bearing phase via pyrotechnic cable 98 that is provided at the forward end of the fairing 90, crossing plane W. Cable 98 is electrically connected to thermal battery 49 via leads 97 and switch mechanism 48.

When activated by means of switch mechanism 48, the cable 98 burns or otherwise breaks, allowing the fairing halves, 90A, 90B, to separate at the nose, and allowing full lateral separation of the fairing halves, 90A, 90B, by application of aerodynamic forces thereon, induced by the forward motion of the projectile 100. As the fairing halves, 90A, 90B laterally separate from one another, the fairing 90 automatically disengages from the head 50 and the body 10, and reaction support previously provided to the head 50 via shoulder 95 is removed, allowing thereafter free relative movement between the head 50 and body 10 via the joint structure 70.

In this embodiment, the switching mechanism 48 is configured for activating the cable 98 by means of one or more of:

-   -   a timer, so that the cable 98 is activated after a predetermined         time has elapsed after launch.     -   an accelerometer or other suitable acceleration sensor or load         sensor (e.g. strain gauge), so that the cable 98 is activated         when acceleration forces acting on the projectile are below a         predetermined threshold, for example considered not to be         potentially damaging to the joint structure 70 if the head 50 is         connected to body 10 via the joint structure 70.     -   a directional sensor, so that the cable 98 is activated when the         projectile is on a trajectory aligned with the target. For         example, regarding a ground target and a ground launcher, the         cable 98 may be activated when the projectile is on a downward         trajectory, such that the velocity vector comprises a downwards         components, i.e., in the direction of the earth.

In one form of operation of the projectile 100, and referring to FIG. 5, the projectile 100 is launched in a conventional manner from a suitable mortar 200, and follows a nominal parabolic trajectory T to a general target zone Z. The specific target X in zone Z is illuminated by an operator OP via a laser beam LB. At launch, and at least for part of the launch phase (T1), in which acceleration loads between the body 10 and head 50 would otherwise potentially damage or destroy the joint structure 70 in the absence of support structure 80, the fairing 90 provides mechanical support between the body 10 and head 50, isolating the joint structure 70 from such acceleration loads. The joint structure 70 may generate its own inertial forces due to acceleration, but these are substantially less than any corresponding loads between the head 50 and body 10, and in any case the joint structure 70 is configured for withstanding its own inertia-induced loads without risk of damage.

Soon after launch, at point T2, the vanes 20 are deployed to provide directional stability.

At a predetermined point T3 in the trajectory T after launch, within the post-launch phase, the fairing 90 is disengaged and removed from the body 10 and head 50, allowing the head to freely align with the velocity vector of the projectile 100. Soon after removal of the fairing 90, or alternatively just before or concurrently therewith, the canards 30 are deployed, and the sensor arrangement in the seeker head is operational. Point T3 is chosen such that the sensor arrangement 60 is pointing in the general direction of the zone Z and in particular the target X, so that the laser-illuminated target X will be in the field of view of at least one of the sensors of sensor arrangement 60. In this manner, the sensor arrangement 60 will then control the canards 30 (T4) to steer the projectile 100 so that this is homed towards the target X (T5).

Point T3 can be chosen in a number of different ways. For example, T3 may be set at a predetermined time after launch, where it is assumed that the projectile 100 has already passed the high acceleration stage and is now in the descent path (or other corresponding path) towards the target. Alternatively, T3 may be defined as the point in the trajectory where the acceleration forces are now not potentially dangerous to the joint structure 70, and thus the fairing 90 may be disengaged, the acceleration forces being monitored by an accelerometer or other suitable sensor. Alternatively, point T3 may be determined according to the attitude of the projectile—a suitable orientation sensor or accelerometer can determine when the projectile 100 is in the descending part of the trajectory T and thus likely to be pointing in the general direction of zone Z, after which the faring may be removed.

Alternatively, the point T3 may be chosen as the point where any two or all three conditions above are met—i.e., (a) not before a predetermined time after launch; and/or (b) when the projectile (in particular the joint structure 70) is no longer subject to potentially damaging acceleration forces; and/or (c) the projectile is in a descending part of the trajectory (or the corresponding final part of the trajectory where the projectile is nominally aligned with the target).

In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not necessarily imply any particular order of performing the steps.

It should be noted that the word “comprising” as used throughout the appended claims is to be interpreted to mean “included but not limited to”.

Whilst some particular embodiments have been described and illustrated with reference to some particular drawings, the artisan will appreciate that many variations are possible which do not depart from the general scope of the invention, mutatis mutandis. 

1-42. (canceled)
 43. A projectile configured for operating at least in a launch phase and in a post-launch phase, the projectile comprising: a projectile body; a projectile head; and a support structure; wherein said projectile head is non-rigidly mounted to said projectile body via a joint structure; wherein said support structure is configured for selectively supporting said projectile head with respect to said projectile body in a load bearing relationship independently of said joint structure during at least a portion of said launch phase, and for selectively terminating said support during at least a portion of said post-launch phase; and wherein at least during said portion of said post-launch phase, said projectile head is freely pivotable with respect to said projectile body in at least two rotational degrees of freedom.
 44. The projectile according to claim 43, wherein said projectile head is at least one of: pivotably mounted to said projectile body via said joint structure; axially movable with respect to said projectile body via said joint structure at least in when said support is terminated; or configured for being freely aerodynamically aligned with said velocity vector of the projectile independently of said projectile body when said support is terminated.
 45. The projectile according to claim 43, wherein said support structure is configured for preventing at least a majority of loads between said projectile head and said projectile body associated with said launch phase being channeled via said joint structure.
 46. The projectile according to claim 43, wherein at least one of the following: said projectile body comprises a front end, an aft end and a first longitudinal axis extending therebetween, and wherein said projectile head comprises a second longitudinal axis, wherein in said load bearing relationship, said first longitudinal axis is substantially coaligned with said second longitudinal axis; in said load bearing relationship, said support structure externally supports said projectile head with respect to said projectile body; in said load bearing relationship, said support structure reversibly interconnects said projectile head with said projectile body and is configured for supporting said loads between said projectile head and said projectile body when thus interconnected; said support structure is configured for being removed from said projectile body and said projectile head at least during said portion of said post-launch phase for selectively terminating said support; or said loads are induced responsive to an acceleration of the projectile during said launch phase.
 47. The projectile according to claim 43, wherein said support structure is further configured for preventing aerodynamic loads being directly applied to said projectile head during said portion of said launch phase.
 48. The projectile according to claim 43, wherein said support structure comprises a load bearing member, wherein in said load bearing relationship said load bearing member is in load bearing contact with said projectile body and in load bearing contact with an external part of said projectile head.
 49. The projectile according to claim 43, wherein said support structure comprises a housing having an open aft end and a cavity in communication therewith, wherein said aft end is configured for reversibly connecting to said projectile body, and wherein said cavity is configured for accommodating said projectile head therein in load bearing contact therewith.
 50. The projectile according to claim 43, wherein at least during said portion of said post-launch phase, said projectile head is freely pivotable with respect to said projectile body in three rotational degrees of freedom.
 51. The projectile according to claim 43, wherein at least one of: said joint structure is configured for permitting relative angular movement between said projectile head and said projectile body, said projectile head being configured for self-alignment with a free stream fluid flow direction, of a fluid through which said projectile is traveling, via said joint structure in said post-launch phase wherein said projectile head is exposed to the fluid flow; said projectile head is gimbaled freely to said projectile body via said joint structure or wherein said joint structure comprises a flexible hose; said projectile head comprises an aft portion comprising an annular tail airfoil configured for providing said self-alignment; or said projectile head is configured for homing said projectile to a target.
 52. The projectile according to claim 43, wherein: said projectile body further comprises a steering arrangement configured for steering the projectile responsive to suitable control input; and said projectile head is further configured for providing said control input at least during said portion of said post launch phase.
 53. The projectile according to claim 52, wherein said projectile head comprises a sensor arrangement configured for sensing a control parameter wherein to generate said control input in response thereto.
 54. The projectile according to claim 52, wherein said steering arrangement comprises an aerodynamic control surface arrangement configured for generating aerodynamic moments suitable for steering said projectile, responsive to said control input.
 55. The projectile according to claim 43, wherein said support structure comprises a casing having an aerodynamically contoured outer wall, and an internal seat for seating an aft portion of said projectile head in said load bearing relationship.
 56. The projectile according to claim 55, wherein at least one of; in said load bearing relationship, said projectile head is immobilized in said casing; or in said load bearing relationship, said casing prevents axial displacement between said projectile head and said projectile body and/or wherein in said load bearing relationship, said projectile head and said projectile body are longitudinally aligned.
 57. The projectile according to claim 55, wherein said casing comprises a first casing half reversibly joined to a second casing half, and wherein said support structure is removable from said projectile head and said projectile body by separating said first casing half from said second casing half
 58. The projectile according to claim 43, wherein said projectile is configured as a mortar shell configured to be launched via a mortar.
 59. A method for operating a projectile, comprising: (a) providing a projectile as defined in claim 43; (b) operating said projectile during at least said portion of said launch phase wherein to selectively support said projectile body with respect to said projectile head via said support structure in a load bearing relationship independently of said joint structure; and (c) selectively terminating said load bearing relationship and subsequently operating said projectile during at least said portion of said post-launch phase.
 60. The method according to claim 59, wherein step (c) comprises removing said support structure from said projectile head and said projectile body while said projectile is traveling in the atmosphere, and allowing said projectile body to become freely aerodynamically aligned with a velocity vector of the projectile independently of said projectile body.
 61. The method according to claim 59, further comprising homing said projectile to a target.
 62. The method according to claim 61, further comprising illuminating said target with an illuminating radiation, detecting with said projectile head said illuminating radiation reflected from the target, and steering said projectile to said target wherein to maintain said reflected illuminating radiation in the boresight of said projectile head.
 63. A method for retrofitting a projectile, comprising: (a) providing the projectile, the projectile comprising a projectile body and a projectile head, wherein the projectile head is non-rigidly mounted to the projectile body via a joint structure; and (b) providing a selectively removable support structure, wherein said support structure is configured for selectively supporting said projectile head with respect to said projectile body in a load bearing relationship independently of said joint structure during at least a portion of said launch phase, and for selectively terminating said support during at least a portion of said post-launch phase, wherein at least during said portion of said post-launch phase said projectile head is freely pivotable with respect to said projectile body in at least two rotational degrees of freedom.
 64. The method according to claim 63, wherein said support structure is configured for preventing at least a majority of loads between said projectile head and said projectile body associated with said launch phase being channeled via or supported by said joint structure, and optionally wherein said majority of said loads is otherwise damaging if applied to said joint structure.
 65. A projectile, comprising: a projectile body; and a projectile head; wherein said projectile head is non-rigidly mounted to said projectile body via a joint structure at a forward end of the projectile body; and wherein said projectile is configured for permitting limited relative axial movement between said projectile body and said projectile head via said joint structure.
 66. The projectile according to claim 65, wherein said joint structure comprises a forward portion configured for pivotingly mounting said projectile head thereto, and an aft portion comprising a shaft slidingly mounted to said projectile body.
 67. The projectile according to claim 66, wherein said shaft is axially reciprocably movable with respect to said projectile body within a displacement range, and wherein optionally a resilient member may be provided for biasing said shaft with respect to said projectile body. 